show me your flex

[chilliwak]

Wow Larry, that is some uber flex!:Wow1: Is there any truth to the idea that half ton pick-ups had a thinner frame and then where more prone to flex as compared to a 3/4 ton frame? Or is this all just bs? Are 1 ton frames thicker than 3/4 ton frames? The question is regarding old style pick-ups like ours. I look forward to hearing your reply. Cheers, Chilli....

 

[Larry]

Chili,

I am not really sure there is any difference between a ½ ton and ¾ frames but the 1 ton frames of this generation definitely have a larger section modulus and RBM (resistance to bending moment). With that, it would make sense that ½ tons and ¾’s would have more frame flex than a 1 ton. Contrary to popular belief, frame flex really isn’t a bad thing. The biggest issue that comes out of excessive frame flex is the risk of cross-member rivets working loose. When they do, just replace them with grade 8 bolts or better yet, replace them with Huck bolts if Huck tooling is available.

You see all of the rage where late model GM frames are very ridged and do not deflect like other trucks. That is great for vehicle ride quality (prevents frame beaming) but in all reality these late model trucks with ridged frames are very brittle, especially when temperatures are below freezing. They don’t bend, they just snap and break like a piece of glass. If you notice, none of the big truck manufactures (medium duty, class 8 trucks, etc.) have jumped on the ridged hydroforming band wagon. Watch a semi launch from a dead stop and see the frame flex like crazy. When the frame is flexing it is not breaking…it is working. An engineer friend from work says frames are a mechanical part of a vehicle much like how bolts are mechanical part where they are really a big spring to retain clamp load. Depending on the application, frames are designed to flex and work like a spring and ultimately be part of the suspension. The frame under pickups of yester-year where just that type of design. Of course, that was before people that started buying pickup trucks that should really be driving cars started complaining of frame beaming and other idiosyncrasies that make pickups, well…..PICKUPS! :sombrero:

 

[mogwildRW1]

True that.

not mine, but a friends Unimog:





All factory except larger tires and beadlock rims

 

[toymaster]

Actually the frame flex was just deemed to be acceptable due to lower manufacturing cost. There was no higher engineering purpose. It is that simple. Any improvements have been to "one up" the competion to gain more of a market share. A competitive advantage if you will. Business is to make the lowest cost product that will serve the target market.

You can try to justify a frame behaving like a wet noodle if you want to but it does not hold water from either a business or engineering point of view.

 

[Larry]

Actually the frame flex was just deemed to be acceptable due to lower manufacturing cost. There was no higher engineering purpose. It is that simple. Any improvements have been to "one up" the competion to gain more of a market share. A competitive advantage if you will. Business is to make the lowest cost product that will serve the target market.

You can try to justify a frame behaving like a wet noodle if you want to but it does not hold water from either a business or engineering point of view.

BS, you apparently do not know any chassis engineers. For light duty pickup trucks, yes….it is about one upping the competition and vehicle ride comfort. For real trucks it isn’t about that, it is about durability. Again, you do not see large severe duty trucks, over the road trucks, etc with ridged frames because they are engineered to flex. In the old days of pickup trucks they didn’t have a need and most likely not the resources to make such a ridged frame like todays light trucks.

 

[toymaster]

Durability?? You have to be kidding me. I will try to get the engineering point across one time. A frame is meant to be a structure not a mechanism, period. You do not build your house on the sand as it were. If it was a mechanism built for durability it would have lubricated points to move upon. The older chevy frames are held together by rivets, due to cost. Ask any chassis engineer you want to improve a vics handling/performance you stiffen the frame wither it is a steel ladder frame or a unibody of sheet metal.

Frame designs, no matter heavy or light Vic, are made to do the work for the least cost. The cost to stiffen a transfer truck frame anymore is not worth the addtional cost. The cab is already isolated and the driver rides on an air ride seat.

Once again a frame is designed to be a structure. On the other hand, suspensions are designed to be mechanisms. Please look up the terms if you do not know the meanings.

Yes, the old chevy light truck frames flex with the suspension although that was never the intent. Just an acceptable side effect. A compromise if you will for profit's sake.

 

[mogwildRW1]

Actually the frame flex was just deemed to be acceptable due to lower manufacturing cost. There was no higher engineering purpose. It is that simple. Any improvements have been to "one up" the competion to gain more of a market share. A competitive advantage if you will. Business is to make the lowest cost product that will serve the target market.

You can try to justify a frame behaving like a wet noodle if you want to but it does not hold water from either a business or engineering point of view.

I can't comment on the domestics, but the Unimog frame is engineered to twist. Everything attached to the frame is 3pt mounted, for torsen free flexing of the frame.





Start at 6:00

http://www.youtube.com/watch?v=fZRews1U1K4&t=6m2s

 

[Larry]

Durability?? You have to be kidding me. I will try to get the engineering point across one time. A frame is meant to be a structure not a mechanism, period. You do not build your house on the sand as it were. If it was a mechanism built for durability it would have lubricated points to move upon. The older chevy frames are held together by rivets, due to cost. Ask any chassis engineer you want to improve a vics handling/performance you stiffen the frame wither it is a steel ladder frame or a unibody of sheet metal.

Frame designs, no matter heavy or light Vic, are made to do the work for the least cost. The cost to stiffen a transfer truck frame anymore is not worth the addtional cost. The cab is already isolated and the driver rides on an air ride seat.

Once again a frame is designed to be a structure. On the other hand, suspensions are designed to be mechanisms. Please look up the terms if you do not know the meanings.

Yes, the old chevy light truck frames flex with the suspension although that was never the intent. Just an acceptable side effect. A compromise if you will for profit's sake.

Whatever :lurk:

 

[2000UZJ]

Before:

After:

In action:

 

[yellocoyote]

 

[Moddz]

8100 lbs of creek!!!





The people who say "Money isn't everything" are lying !!

 

[getlost4x4]

 

[getlost4x4]

my old ML430.



:elkgrin:

 

[notajeep]

This is my non-expo ride.

 

[notajeep]